A flat-plate-shaped device under test such as an integrated circuit formed on a semiconductor wafer, an integrated circuit diced from a wafer, or the like, undergoes an electrical test with use of an electrical connecting apparatus such as a probe card to determine whether or not the integrated circuit functions in accordance with the specification. At the time of such an electrical test, the device under test is thrust at its electrodes by probe tips of contacts of the electrical connecting apparatus and is supplied with electrical signals in this state. This is shown generally in Japanese National Patent Appln. Public Disclosure No. 2008-145238 and Japanese National Patent Appln. Public Disclosure No. H10-206463, which are incorporated by reference.
In a testing apparatus using the electrical connecting apparatus of this kind, it is important that the probe tip of each contact is opposed to the corresponding electrode of the device under test and that a virtual plane formed by the probe tips of the plural contacts is parallel to a test stage in order to obtain accurate test results.
Accordingly, the testing apparatus has an alignment function of detecting coordinate positions of plural marks such as alignment marks provided on the electrical connecting apparatus by a detecting unit provided on the test stage receiving the device under test to determine the two-dimensional coordinate position or three-dimensional coordinate position of each mark and relatively displacing the electrical connecting apparatus and the test stage based on the determined result to align the probe tip of each contact with the corresponding electrode of the device under test.
The electrical connecting apparatus used in the testing apparatus having the above alignment function is exemplified by one that uses the probe tip itself of the contact as a mark (Japanese National Patent Appln. Public Disclosure No. 2008-175762, which is incorporated by reference), one in which a mark is formed in proximity to the probe tip (Japanese National Patent Appln. Public Disclosure No. 2005-533263 (WO2004-15432), which is incorporated by reference), and one in which a mark is provided at a member other than the contact (Japanese National Patent Appln. Public Disclosure No. 2007-278859, which is incorporated by reference).
In any of the above testing apparatuses, light is irradiated from the detecting unit toward the mark, and the reflected light from the mark is detected at the detecting unit to identify the mark and determine the coordinate position of the mark.
However, in the above conventional apparatuses, since the output signal of the detecting unit is inevitably influenced to a great extent by the incident light to the detecting unit reflected from the surrounding area of the mark although the amount of the reflected light from the mark is small, the mark cannot be identified accurately, and thus it is difficult to determine an accurate coordinate position of the mark.